VM do have UK call centres, but it seems the vast majority of support and basic enquiries are handled by offshore call centres run under contract (by an outfit called Tech Mahindra in India, I think, and I think some are shipped further out to the badlands of Indonesia's cheapest service centres). There's no sure fire way of speaking to the UK call centres, although it will come as no surprise that the majority of sales and customer retention calls are handled by UK call centres.
Since you've evidently not started the contract, you might want to consider cancelling now because the service standards you're been encountering are sadly representative of what you'll experience if you need to speak to VM when the contract starts.
VM's great when everything works and you don't need to speak to anybody. When things don't work, you're locked into a long fixed term contract, and you need to speak to someone...well, it's all a bit different.
